Satellite radioterminal communication systems and methods are widely used for communicating among radioterminals and/or among radioterminals and wire-line terminals. As is well known to those having skill in the art, a satellite radioterminal communication system includes a space segment, which includes one or more satellites and one or more gateways. The satellite(s) communicate with radioterminals over a plurality of service links and communicate with the gateway(s) over one or more feeder links using one or more antennas at the satellite(s).
As used herein, the term “radioterminal” includes cellular and/or satellite radioterminals with or without a multi-line display; Personal Communications System (PCS) terminals that may combine a radioterminal with data processing, facsimile and/or data communications capabilities; Personal Digital Assistants (PDA) that can include a radio frequency transceiver and a pager, Internet/Intranet access, Web browser, organizer, calendar and/or a global positioning system (GPS) receiver; and/or conventional laptop and/or palmtop computers or other appliances, which include a radio frequency transceiver. As used herein, the term “radioterminal” also includes any other radiating user device/equipment/source that may have time-varying or fixed geographic coordinates, and may be portable, transportable, installed in a vehicle (aeronautical, maritime, or land-based), or situated and/or configured to operate locally and/or in a distributed fashion at any other location(s) on earth and/or in space. A “radioterminal” also may be referred to herein as a “radiotelephone,” “terminal” or “wireless user device”.
These radioterminals can include satellite-only radioterminals and/or multi-mode satellite/terrestrial radioterminals. The multi-mode satellite/terrestrial radioterminals may be configured to communicate with an ancillary terrestrial network using one or more satellite frequencies.
Satellite radioterminal communications systems and methods that may employ terrestrial reuse of satellite frequencies are also described in U.S. Pat. No. 6,785,543 to Karabinis, entitled Filters For Combined Radiotelephone/GPS Terminals, and Published U.S. patent application Nos. US 2003/0054761 to Karabinis, entitled Spatial Guardbands for Terrestrial Reuse of Satellite Frequencies; US 2003/0054814 to Karabinis et al., entitled Systems and Methods for Monitoring Terrestrially Reused Satellite Frequencies to Reduce Potential Interference; US 2003/0054762 to Karabinis, entitled Multi-Band/Multi-Mode Satellite Radiotelephone Communications Systems and Methods; US 2003/0153267 to Karabinis, entitled Wireless Communications Systems and Methods Using Satellite-Linked Remote Terminal Interface Subsystems; US 2003/0224785 to Karabinis, entitled Systems and Methods for Reducing Satellite Feeder Link Bandwidth/Carriers In Cellular Satellite Systems; US 2002/0041575 to Karabinis et al., entitled Coordinated Satellite-Terrestrial Frequency Reuse; US 2002/0090942 to Karabinis et al., entitled Integrated or Autonomous System and Method of Satellite-Terrestrial Frequency Reuse Using Signal Attenuation and/or Blockage, Dynamic Assignment of Frequencies and/or Hysteresis; US 2003/0068978 to Karabinis et al., entitled Space-Based Network Architectures for Satellite Radiotelephone Systems; US 2003/0153308 to Karabinis, entitled Staggered Sectorization for Terrestrial Reuse of Satellite Frequencies; and US 2003/0054815 to Karabinis, entitled Methods and Systems for Modifying Satellite Antenna Cell Patterns In Response to Terrestrial Reuse of Satellite Frequencies, US 2004/0121727 to Karabinis, entitled Systems and Methods For Terrestrial Reuse of Cellular Satellite Frequency Spectrum In A Time-Division Duplex Mode, US 2004/0192293 to Karabinis, entitled Aggregate Radiated Power Control For Multi-Band/Multi-Mode Satellite Radiotelephone Communications Systems And Methods, US 2004/0142660 to Churan, entitled Network-Assisted Global Positioning Systems, Methods And Terminals Including Doppler Shift And Code Phase Estimates, and US 2004/0192395 to Karabinis, entitled Co-Channel Wireless Communication Methods and Systems Using Nonsymmetrical Alphabets, all of which are assigned to the assignee of the present invention, the disclosures of all of which are hereby incorporated herein by reference in their entirety as if set forth fully herein.
For a given size of an antenna feed network (e.g., for a given number of antenna feed elements), as the antenna size (e.g., the reflector diameter) of a satellite antenna grows, the geographic area that can be served subject to a specified performance index (such as a specified satellite antenna gain over noise temperature (G/T)) generally becomes smaller. In order to increase the geographic area that can be served by a given satellite antenna size (subject to a specified satellite performance index) the size of the antenna feed network may have to be increased. This may be prohibitive, in some applications, where the size, mass and/or heat dissipation of a satellite has exceeded a certain limit. Growing the size of an antenna feed network may also require additional signal processing by the satellite payload which may further aggravate the size, mass and/or heat dissipation constraints of the satellite.